It is certain from observations I have made, corroborated by experience gained in the laboratory, that iron at a high temperature and under great pressure--conditions existent at great depths below the surface of the earth--acts as the long-sought solvent for carbon, and will allow it to crystallise out in the form of diamond. But it is also certain, from the evidence afforded by the Arizona and other meteorites, that similar conditions have existed among bodies in space, and that on more than one occasion a meteorite freighted with jewels has fallen as a star from the sky. INDEX Able, Sir F., closed vessel experiments, 122 Absorption spectrum of diamond, 101 Aliwal North, 6 Alluvial deposits of diamonds, 9 Amygdaloidal trap, 10 Arizona meteor, 136 Arkansas, diamonds in, 2 Ash of diamond, 82, 89 Augite, 20 Automatic diamond collector, 56 Barytes, 71 -- density of, 93 Basalt, 15 Basutos, 12, 39 Bechuanas, 12, 39 Beryl, density of, 93 -- refractive index of, 103 Biotite, 20 Blackening of diamonds, 98 Blue ground, 10, 47 -- -- diamantiferous, 18, 19 Boart, 81, -- combustion temperature of, 90 -- density of, 93 Boiling-point of carbon, 110 Bonney, Rev. Professor, 67 Boyle on the diamond, 100 Brazil, diamonds in, 4 Breakwater, Cape Town, 36 Breccia, diamantiferous, 19 Brilliant cut diamond, 102 British Association in South Africa, 7 British Guiana, diamonds in, 4 Bronzite, 20, 71 -- hydrated, 19 Bultfontein Mine, 14 -- -- characteristics of diamond from, 64 Bursting of diamonds, 105 Calcite, 20, 97 California, diamonds in, 3 Canada balsam, refractive index of, 103 Canyon Diablo meteorite, 136 Cape Colony, 5 Cape Town, 5 Carat, equivalent in grains, 69 Carbon, boiling and melting point of, 110 -- combustion temperature of, 90 -- critical point of, 110 -- density of, 93 -- dissolved in iron, 116 -- volatilisation of, 115 Carbonado, 81 -- density of, 93 Characteristics of diamonds from the different mines, 64 Chemical properties of diamond, 89 Chromate of lead, refractive index of, 103 Chrome diopside, 71 -- iron, 20 -- -- ore, 71 -- -- -- density of, 93 Chromite, 20 Classification of rough diamonds, 73 Cleavage of diamonds, 78 Coke, density of, 93 Colesberg Kopje, 26 Collecting the gems, 55 Coloured diamonds, 62, 82 Combustion of diamond, 89 -- temperatures of diamond, boart, graphite, and carbon, 90 “Comet” crushers, 49 Compound system, 36, 37 Concentrating and washing machinery, 49 Convict labourers, 71 Cordite, diamond from explosion of, 123 Corundum, 20 -- density of, 93 Cradock, 6 Craters or pipes, 18 Crown glass, refractive index of, 103 Crusher, “Comet,” 49 Crystallisation of diamond, 86 Crystals, octahedra, of diamond, 63, 86 Cullinan diamond, 15, 76, 80, 104 Dallas, Captain, 40